In an optical communications system, data may be transported via digital signals over optical channels. A digital signal processor (DSP) may be provided to receive a particular digital signal, via a particular optical channel, and modulate the digital signal (e.g., based on bits associated with the data) to represent the data, associated with the digital signal, as symbols. The modulated digital signal can be provided to an analog to digital converter to provide corresponding analog signals to a modulator. The modulator may modulate a phase of a reference signal to form an output data signal (e.g., to convey the data over a carrier wave associated with the reference signal).
A receiving device may receive the output data signal and may compare the phase of the output data signal to a local reference signal. Based on the difference between the phase of the output data signal and the phase of the local reference signal, the receiving device may recover the data associated with the output data signal.
A DSP may modulate a digital signal based on a particular modulation format, (e.g., quadrature phase shift keying (QPSK), binary phase shift keying (BPSK), 16 quadrature amplitude modulation (16QAM), 32QAM, or the like). A particular modulation format may have particular advantages/disadvantages with respect to another modulation format. For example, some modulation formats may offer higher bit rates in exchange for lower transmission range. Also, different modulation formats may have different associated costs (e.g., licensing costs, transmission costs, etc.).